Either of the other two options returns a SQL error, which shows up in error.log as:
Text Formatted Code
Mon 16 Jun 2008 23:40:43 EDT - 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '-50, 50' at line 1. SQL in question: SELECT * FROM gl_http_referer_phrases ORDER BY counthits DESC LIMIT -50, 50